The “Father of Modern Philosophy”, René Descartes (1596–1650) was one of the most prominent voices of the Scientific Revolution. A key philosopher of the 17th century, he developed a connection between algebraic logic and philosophical concepts—a practice that would eventually lead to the creation of modern philosophic study. His landmark works such as Meditations on First Philosophy established him…

René Descartes

French physicist, philosopher, and mathematician, commonly referred to as the “Father of Modern Philosophy.”

Main accomplishments:

Developed the concept of Cartesian geometry, which used algebraic symbols and logic to represent geometric concepts. Cartesian geometry was one of the earliest efforts to push towards “universal mathematics.” The term “Cartesian” is now applied to several different branches of mathematics.

Wrote several discourses on mathematics and philosophy, including his three most famous works: Discourse on the Method (1637), La Géométrie (1937), and Meditations on First Philosophy (1641). It was in Part IV of Meditations that he coined the phrase “Cogito ergo sum,” or in English, “I think, therefore I am.”

Among the first to apply mathematic concepts to science and philosophy, using logic and reason to tackle philosophic queries; this laid the bedrock for modern methods of philosophical study.

Provided the first systematic account of the metaphysical connection between the mind and the body, known as “dualism.” Commonly credited as the founder of reflex theory, which accounted for the automatic human reflex to sensations such as pain (recoiling away from fire without thinking about it, for example).

EARLY LIFE

The son of a French judge, René Descartes studied law at his father’s behest but was never a practicing lawyer. Of all the unlikely things to do after law school, he actually became a mercenary soldier in 1618, during the Thirty Years War that was fought among most of the European powers over the territory of the German states—a war that originated predominantly from a Catholic/Protestant conflict. Descartes fought for the United Provinces of Netherlands and intended to leave temporarily behind the life of letters to see the world. It’s uncertain in what capacity he served, but there’s a good chance he served in the Corps of Engineers, constructing and maintaining the artillery of the day.

During a temporary truce, Descartes was living a peaceful life in a small village on the banks of the Danube when he experienced three dreams that propelled him towards mathematics and philosophy. He soon found himself thinking about the relationship between mathematics and physics, and by 1622 he had finished his military career, returning to France for a few years before moving to the Netherlands, where he spent most of his life and wrote most of his major work.

BRIDGING THE GAP BETWEEN MATH AND PHILOSOPHY

His “Treatise on the World,” sometimes referred to by its French abbreviation “Le Monde”, was written between 1629 and 1633, and was intended as a complete overview of his philosophy as he had then formulated it, with a particular emphasis on what was then called natural philosophy (the modern sciences of physics, chemistry, and biology). But Descartes subscribed to the Copernican view of the cosmos—which had the Earth revolving around the Sun, not the other way around, in contrary to Catholic teaching. Galileo had just been excommunicated for those very views, and so Descartes put “Le Monde” aside for the time being. It was eventually published decades after his death though substantial parts of it had been revised in the interim and published as parts of other works.

He immediately began work on his Discourse on the Method of Rightly Conducting the Reason and Searching for Truth in the Sciences, which was to become one of the cornerstones of modern science. Descartes’ aims in this book are made clear by the first chapter title: “How To Think Correctly.” It was not enough to be intelligent, Descartes said—a good mind, like a healthy body, still had to be used correctly. From there, he calls for rigor in the scientific method, including a focus on experimentation—the same standards adhered to today, but flouted for most of history. Above all, be skeptical, Descartes advised. Accept as true nothing you are not certain of and to become certain, test the claim as strictly as possible. This was an especially influential recommendation on the scientists and philosophers to come after him.

One of the appendices in the Discourse is La Geometrie, which introduced the Cartesian coordinate system familiar to all geometry students (you remember all that graph paper, plotting x and y coordinates). Descartes was the first to combine algebra and geometry into the discipline of analytic geometry, which was a stepping stone towards the development of Newton and Leibniz’s calculus.

By focusing so much on the method, Descartes managed to contribute to the sciences that outlived his era. Particular discoveries in science are so often refined, reformulated, disproven, that it is a rare scientist—a Newton, an Einstein, a Darwin—who makes such a contribution that remains relevant centuries later. But the methodology is sound even once our understanding of the facts has changed. The foundation of his method, that skepticism, and demand for a rigorous proof, is applicable to all sciences—like a sturdy box that will perform equally well no matter what you put into it. “Cogito ergo sum” comes out of this discussion of methodology too: the full quote is “Dubito, ergo Cogito, ergo sum.” I doubt, therefore, I think, therefore, I am: Descartes argues that because he is skeptical, he is thinking; because he is thinking, he must exist. But everything else must be proven. Even the senses can be deceived, so the only thing that can be known beyond a shadow of a doubt is his own existence as a thinking person.

This discussion, in turn, led to Descartes’ formulation of what cognitive science calls “the mind-body problem.” Like many of the continental rationalists—a popular school of philosophy in his day—Descartes saw the body as a machine; advances in anatomical study of humans and animals had led to a better understanding of how musculature and the cardiovascular system worked, for instance. But the mind—or soul, a term used pretty interchangeably in philosophical writings of the time—was without material existence; the brain was not well understood, and because Descartes thought only humans had pineal glands, he saw that gland as the physical “seat” of the soul, whose operations were otherwise not limited by physical mechanism. In this, his science was clearly wrong—but cognitive science continues to pursue the matter of interactions between the nonmaterial mind and the physical body.

“Le Monde” and its sequel “L’homme” (Man) were published after Descartes’ death but were his earliest major works, presenting the fundamental aspects of his philosophy. Discourse on the Method follows, and his thoughts on mind-body dualism are further explored in Meditations on First Philosophy and The Description of the Human Body, though at times his remarks are informed by since-disproved beliefs about human anatomy. An especially interesting work is Passions of the Soul, which combines Descartes’ mind-body dualism with the philosophical tradition of expounding on the nature of “passions” or emotions. This work was dedicated to his student, Princess Elizabeth of Bohemia, a lifelong patron of the arts and sciences.

LATER LIFE

Descartes died in 1650 while serving in Sweden as a tutor for the Queen. He seems to have struggled with and succumbed to pneumonia in his last days, possibly as a result of overworking himself. A dozen years after his death, his books were condemned by the Catholic Church as he had often feared might happen. Nevertheless, he remained an important figure in science—never needing to be “rediscovered,” as Descartes’ works simply never went away. The breadth and depth of his contributions to modern thought are rivaled only by such giants as Newton and Leonardo da Vinci.

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